The primary focus of these studies is the coordination between the synthesis and assembly of the intracellular membranes of the secretory pathway and the induction of active immunoglobulin secretion in lymphocytes. The rates of synthesis of proteins of the endoplasmic reticulum (ER) will be measured in control and mitogen-tested murine lymphocytes. These studies will help to determine the magnitudes of the increases in the synthesis of the ER proteins and whether there is a temporal order in the synthesis of these proteins. They are also intended to provide insights as to the relative contribution of transcriptional and translational control to the expression of the genes for the ER proteins. In addition, assays for immunoglobulin precursor cleavage and core glycosylation will be used to measure these processing functions in the ER from control and mitogen-treated lymphocytes. These studies will determine to what extent changes in these functions occur and in what order. They will also allow correlations to be made between the structure, composition, and processing activity of the endoplasmic reticulum. In order to complement the above studies, it is planned to study cells with mutations in processing functions. Methods designed to obtain temperature sensitive mutants of the proteins modification activities of lymphoid cells are described. The information obtained from all of these studies will contribute direct evidence for the role of a particular ER function in nascent protein processing and allow the eventual assignment of a particular function to a specific membrane component.